1. Field of the Invention
The present invention relates to a database system for reorganizing a database and more specifically to a technology effectively applicable to a database system that resolves a disturbance of data areas in a round-the-clock operational relational database management system (RDBMS).
2. Description of the Related Art
With rapid advances in e-business and other related areas in recent years, there is a growing need for a round-the-clock operation of database management systems. In a database management system, data stored in the system becomes disarranged or fragmented over time as transactions continue. It is therefore necessary to stop accesses to the database and reorganize the stored data. However, the 24-hour continuous operation does not permit a halt of database access. For this reason, as a substitute means for database reorganization, processing has come to be implemented which eliminates a disturbance of data areas without blocking access to the database.
Such a disturbance resolving method, however, has its limitations and undesired influences. That is, this method is either applicable only to limited kinds of disturbance resolution, such as forwarded row reclamation processing that collects so-called forwarded rows or data stored in a plurality of storage areas, or it imposes a heavy burden on other processing being executed in the database management system. Since single disturbance resolution processing cannot function as a perfect substitute means for database reorganization as described above, some database management systems use multiple kinds of disturbance resolution processing so that appropriate processing can be selected to deal with different situations and purposes. In such systems, it is important to make a correct decision on which of the multiple kinds of disturbance resolution processing should be selected and executed under what circumstance.
As to the conventional single means for reorganization, a method has been disclosed which checks the current state of data areas to see if the database needs to be reorganized and automatically executes reorganization processing as necessary. More specifically, the method involves checking whether there is a data file in excess of allowable size of use and, if so, automatically executing the database reorganization processing (see JP-A-11-161525 (page 5, FIG. 6)).
In a system that has multiple kinds of disturbance resolution processing to deal with different situations and purposes, it is essential to correctly determine which of the multiple disturbance resolution processing should be selected for execution under what circumstance. To make this decision correctly requires a frequent execution of an analysis on the state of database storage areas, which in turn increases a load to be processed. This conventional method, however, provides no satisfactory solution to the increased processing load caused by the status analysis. Further, the conventional method of automatically executing a reorganization does not disclose any means for selecting the optimum from multiple disturbance resolution processing. These problems of the conventional methods still remain to be solved.